Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Photo: Bay City News Service

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Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Photo: Bay City News Service

Image 3 of 4

Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Items taken from some of the 22 protesters who were arrested in San Francisco on Saturday, Oct. 6, 2012.

Photo: Bay City News Service

Image 4 of 4

22 demonstrators arrested in S.F.

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One police officer was slightly injured and 22 demonstrators were arrested Saturday as demonstrators briefly disrupted traffic with an unannounced march through San Francisco's downtown.

Some of the people arrested were carrying hammers, an ice pick, road flares and bags of paint and rocks, said Officer Gordon Shyy, a police department spokesman.

The trouble started just before 3 p.m. when about 100 marchers, many of them wearing masks and black clothing, gathered at Justin Herman Plaza and began marching west down Market Street, tying up traffic.

When police told them they had no permit for the march and needed to get out of the street, the marchers began tossing flares, bags of paint and other objects at the officers, Shyy said. One police officer was struck in the head and received minor injuries, while several other officers were bathed in paint.

Police stopped the march in the Financial District, shortly after 3:30 p.m. They circled a number of demonstrators at California and Battery streets, and they arrested other demonstrators as they fled to Pine and Sansome streets, Shyy said.

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At least some of the marchers face felony charges of assault on a police officer, while others were arrested for conspiracy, riot, resisting arrest and failure to obey a lawful order from a peace officer.

While police were busy at events across the city Saturday, plans always include extra officers to handle any unanticipated problems that might develop, Shyy said.

"We know there are always possible demonstrations in the city and we prepared for that," he said.